The present invention relates to anti-runway bombs equipped with a downward or acceleration propulsive unit and, more generally, bombs intended to damage high mechanical resistance surfaces such as aerodrome runways used for taking off and landing of aircraft.
Referring to FIG. 1, an operating mode of antirunway bombs known up to now is shown by aircraft 1 and the trajectory shown with broken lines T1, appearing in the lower part of the diagram. The operating principle is the following. The aircraft 1, with or without pilot, flies over the runway or strip 2 to be damaged and releases one (or more) bombs. The aircraft continues its travel independently of that of the released bomb 3. The bomb subjected to the Earth's gravity, to air resistance and to the speed acquired on board the aircraft, describes the trajectory referenced T1. Bomb 3 is equipped with a parachute braking system 4. Once its speed is sufficiently close to the vertical, a downward propulsive unit is activated for driving and accelerating the fall of the bomb, and increasing the impact energy of the latter on the runway 2.
This operating procedure will no longer be possible in the short term:
on the one hand because of the improvement in the means for detecting firing from air-air defence systems which will force aircraft to fly over their objectives at a very low altitude (less than 50 m),
on the other hand because of the improvement in penetration resistance of runways which will compel bomb constructors to confer thereon a higher kinetic energy.
Now, the above described operating procedure causes a loss of altitude of 30 to 40 m at the end of the parachute braking phase. If the release altitude is less than 50 m, there is not enough height for operating a propulsive unit from which an even higher power is expected. In fact, the operating height of the propulsive unit is equal to (V.sub.o +V.sub.1 /2) .times.T where V.sub.o is the vertical component of the initial speed at the time of ignition of the propulsive unit, V.sub.1 the final speed of the propulsive unit and T the combustion time. Now, V.sub.1 must be sufficiently high so as to obtain the kinetic energy required for piercing the runway, e.g. 350 m/s. Furthermore, in the present state of the art, a propulsive unit cannot be constructed operating with a combustion time less than 0.20s having acceptable dimensions and a moderate cost price. In the example cited, if V.sub.o =10 m/s and V.sub.1 =350 m/s, the propulsion height is 36 m, and if only 10 to 20 m are available another solution must then be found for the propulsive unit to be fully efficient.
The object of the invention is to overcome these drawbacks by providing an anti-runway bomb operating with a different operating mode and keeping an essential property of the operation : accuracy.
The invention provides an anti-runway bomb intended to be released at very low altitude, equipped with a downward propulsive unit, further comprising means for braking and orienting said bomb during its initial fall, so as to position the bomb in a plane activating an upward propulsive unit.